Knowing when to plant mums in ground is the single most important factor for their long-term survival. Get the timing right, and you’ll be rewarded with hardy, vibrant plants that return bigger and better each year. This guide cuts through the confusion to give you the clear, actionable advice you need for success.
When To Plant Mums In Ground
The absolute best time to plant hardy garden mums in the ground is in the spring. This gives the plant’s roots an entire growing season to establish themselves before winter arrives. Planting in spring allows the mum to focus on growing a strong, deep root system instead of just producing flowers.
Fall planting is what most people see at garden centers, but it’s actually risky for the plant’s survival. Those beautiful, bloom-covered pots are meant for instant color. If you plant them in the ground in fall, they often don’t have enough time to root deeply before the ground freezes.
Why Spring Planting is Non-Negotiable
Think of a mum planted in spring versus one planted in fall. The spring-planted mum has months to settle in. It can handle summer heat and drought much better. When winter comes, it’s snug and secure underground.
The fall-planted mum is in a race against the clock. Its energy is going to those pretty blooms you bought it for. The roots remain shallow and weak. A hard frost can easily heave the whole plant right out of the soil, which is a common cause of death.
The Second-Best Window: Early Summer
If you miss the spring window, early summer is your next best option. Aim to get them in the ground by mid-June to early July at the latest. This still provides a good couple months for root growth before blooming begins.
The key is to avoid the stress of peak summer heat. If planting in summer, be extra vigilant about watering. You might also need to pinch them back to encourage bushiness, which we’ll cover later.
What If You Only Have Fall Mums?
Don’t despair if you already bought fall mums! You have two good options:
- Treat them as annuals: Enjoy their fantastic display in pots or in the ground until the season ends.
- Overwinter them strategically: After blooms fade, trim the stems down to about 4 inches. Mulch the plant very heavily with several inches of straw or shredded leaves. In spring, remove the mulch and see if new growth appears. Sometimes they survive, but it’s not guaranteed.
Step-by-Step Guide to Planting Mums
Once you’ve got the timing down, proper planting technique makes all the difference. Follow these steps for the best results.
1. Choose the Right Plant
Look for labels that say “hardy garden mum” or Chrysanthemum morifolium. Avoid plants that are already completely covered in open blooms; instead, choose ones with lots of tight buds. The foliage should be deep green and healthy, with no signs of wilting or bugs.
2. Pick the Perfect Spot
Mums need two things to thrive: sun and well-drained soil. Choose a location that gets at least 6 hours of direct sunlight each day. Good drainage is critical, as mums will rot in soggy soil. If your soil is heavy clay, amend it with compost or plant in a raised bed.
3. Planting Your Mum
- Dig a hole that’s twice as wide as the root ball and just as deep.
- Mix some compost into the soil you removed.
- Gently remove the mum from its pot and loosen the roots if they are pot-bound.
- Place the plant in the hole, ensuring the top of the root ball is level with the soil surface.
- Backfill with your soil-compost mix and firm it gently around the base.
- Water thoroughly to settle the soil and eliminate air pockets.
4. Immediate Aftercare
Space plants about 18-24 inches apart to allow for air circulation. Apply a 2-inch layer of mulch around the base (but not touching the stems) to conserve moisture and regulate soil temperature. Water regularly for the first few weeks until you see new growth, a sign the roots are establishing.
Essential Care for Healthy, Hardy Mums
Planting at the right time is 80% of the battle. These ongoing care tips will ensure your mums become permanent, flourishing parts of your garden.
Watering and Feeding
Mums like consistent moisture but hate wet feet. Water deeply when the top inch of soil feels dry. Avoid overhead watering which can promote disease; water at the base instead. Feed them with a balanced, all-purpose fertilizer in early spring as growth resumes, and again in early summer. Stop fertilizing by August to avoid encouraging tender new growth before frost.
The Secret to Bushy Plants: Pinching
To prevent tall, leggy mums that flop over, you need to pinch them. This simple practice encourages branching and many more flowers.
- Start in late spring when the stems are about 6 inches tall.
- Using your fingers or shears, remove about 1 inch of the growing tip from every stem.
- Repeat this process every 2-3 weeks until around the 4th of July.
- After that, let the plant develop its flower buds for fall.
This might feel counterintuitive, but it’s the trick for a spectacular, dense display.
Winter Preparation
Even spring-planted mums benefit from a little winter protection. After the first hard frost blackens the foliage, you can cut the stems back to 3-4 inches above the ground. Apply a fresh, thick layer of mulch (like straw or shredded leaves) over the crown of the plant. This insulates the roots from freeze-thaw cycles. Remove the mulch in early spring as new shoots begin to appear.
Common Problems and Simple Solutions
Even with great care, you might encounter a few issues. Here’s how to handle them.
- Leggy Growth / Few Flowers: This is almost always due to insufficient sunlight or a lack of pinching. Move the plant to a sunnier spot next spring and commit to the pinching schedule.
- Center Dies Out: Mums can get woody in the center after a few years. The fix is easy: every 2-3 years in early spring, dig up the clump, divide it into several smaller pieces with a shovel or knife, and replant the healthy outer sections.
- Powdery Mildew: This white fungus on leaves is common, especially with poor air circulation. Ensure proper spacing, water at the base, and choose mildew-resistant varieties. Neem oil can help treat an existing infection.
FAQ: Your Mum Planting Questions Answered
Can I plant potted mums in the ground in October?
You can, but their chance of surviving the winter is low. They are better treated as annuals at that point. For permanence, plan to buy and plant in the spring.
How do I get my mums to come back every year?
The formula is simple: plant hardy varieties in the spring, in full sun with good soil, pinch them until July, and provide winter mulch. Strong roots are the foundation of their return.
What is the latest month you can plant mums?
For reliable overwintering, aim to have them in the ground by mid-July at the absolute latest. This gives roots about 8-10 weeks to grow before blooming energy takes over.
Should you cut back mums in the fall or spring?
You can do either. Many gardeners cut them back after a hard frost in fall for tidiness. Others leave the dead stems to provide a bit of extra winter protection and cut them back in early spring. The plant doesn’t mind which you choose.
By focusing on the critical factor of timing—prioritizing spring planting—you set your mums up for a lifetime of success. Remember, patience is key. A mum planted this spring may not look like much at first, but by next fall, it will have transformed into a robust, floriferous clump that will grace your garden for seasons to come. With the right start and simple care, you’ll enjoy the rich, autumnal colors of hardy mums year after year.